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After OCR: check formulas, footnotes and reading order in technical PDFs

A practical acceptance checklist for scanned textbooks and papers, covering mathematical symbols, note references, tables and multicolumn text.

A paragraph with one mistaken letter may still be understandable. A formula with one mistaken sign may no longer mean the same thing. Technical documents therefore need a different acceptance check from ordinary prose.

Do not judge the result only by whether the conversion finished or whether the page looks tidy. Check the relationships between symbols, labels and surrounding explanations.

Separate recognition from translation

Recognition turns marks in a scan into text or structured content. Translation then works with that result. If OCR has already mistaken a minus sign for a dash or dropped a subscript, a later translation step cannot be trusted to reconstruct the intended mathematics.

PDF Craft supports document recognition and conversion workflows, with options relevant to formulas and footnotes. Formula preservation should mean retaining recognized expressions where supported, not an assurance that the original scan was read without errors.

For difficult material, first inspect a converted sample in the PDF workspace before adding translation.

Check symbols against the page image

Choose an equation that contains several features: subscripts, superscripts, fractions, a Greek letter or a summation range. Compare it with the original rather than with what you expect the equation to say.

Pay attention to pairs such as zero and the letter O, one and lowercase l, or multiplication and the letter x. Check bracket pairing, minus signs and decimal separators. Verify that an equation number has not become part of the expression.

If the result uses a math representation, preview it in the actual destination reader or editor. A correct expression can still display poorly when the viewer does not support the same notation.

Follow each note in both directions

A footnote is a relationship between a marker and its explanation. Select several markers in the main text, locate the corresponding notes and confirm that the numbers or labels match.

Then read the notes themselves. A page footer can be mistaken for body text; a short footnote can be dropped; a long note can be split at a page boundary. Even if links are present, inspect the text they connect.

Decide whether notes are necessary for your task before selecting processing options. For scholarship, omitting a note may remove a qualification or a source citation.

Inspect tables and column order

Read one complete paragraph that crosses a column boundary. The output should finish the intended column before jumping to the next. Compare table values with their row and column labels, including unit headings.

A useful review record has four columns:

Source locationElementWhat to compareResult
Chapter sampleEquationSymbols, indices, boundsAccept or correct
Note sampleReferenceMarker and full noteAccept or correct
Table sampleDataValue, label and unitAccept or correct

Fill it with actual observations. Do not convert a few inspected examples into an invented document-wide accuracy percentage.

Decide whether to accept or reprocess

If problems concentrate in faint scans or distorted pages, seek a better source. If the output is correct but the renderer is not, test another reader or format before paying to process the source again.

For Markdown, consult the research workflow. For continuous reading, consult the EPUB conversion guide. Keep the original beside the result whenever formulas, footnotes or citations carry the main meaning.

Put the guide into practice

Start with a representative file, review the result, then use the workflow that fits your documents.

Open the workspace